The present invention relates to medical technology. More particularly, this invention is concerned with an injection apparatus for hypodermic injections wherein a plurality of different liquid medicaments can be used, especially for the self-injection of insulin by diabetics.
Insulin treatment is still characterized by injection from syringes, the insulin being drawn out of small medicine bottles, into which unsterile air is blown in the process, and to which an antibacterial substance has been added. It often happens that small air bubbles with the syringe are overlooked, or, when detected, they can only with difficulty be eliminated by tapping, while the canula is being held with the point upwards. Many patients, particularly when their vision is impaired by age or disease, cannot clearly read the syringe scale. Other patients do not have the strength to overcome the friction of the piston; and still others have serious difficulties, for example, with the lack of friction in long-stroke syringes, in that they unintentionally empty part of the contents. For novices, there are the problems of fear of the needle and clumsiness in handling. The preparation of syringes and the execution of injection have certain spatial and material preconditions. Hitherto existing suction injectors have generally been used on animals. Little regard was made to sterility. Besides that, the devices were too large and difficult to use. Great effort and space were needed to produce the vacuum. There are injection apparatuses for insulin on the market which work by underpressure without a cannula, but they are in reality useless. The pressurized stream of medicine destroys tissue to a considerable extent and leads, when used daily, almost regularly to serious skin irritations. The painfulness of this method exceeds that caused by use of modern cannulas. Besides that, the nozzles become clogged by the protein solution and have to be carefully cleansed. The supply bottles are still filled with unsterile air for the replacement of volume. The recently introduced insulin pumps for the continuous dosing of old insulin promise to be for many years to come a solution of the problem for only a limited group of patients and even then only for limited periods. The pumps, which are carried on the body, require a problematical connection with the blood stream or with the lower skin tissue, for example to the abdominal cavity, thus presenting a potential source of infection. Even devices with sensors for measuring the amount of sugar in the blood implanted in the body, even if they are one day developed to the point where they function perfectly, present the problem, that an automatic dosing of insulin, whenever the level of sugar in the blood rises, would increase the appetite, which itself would have a negative effect on problems, such as overweight and arteriosklerosis, which are connected with diabetes. There is also the danger of hypoglycemia, especially at night, with the consequence of irreparable brain damage. Other hormonal and metabolic variables, as for example the level of lactic acid during muscular exertion, would have to be taken into account. A specified daily routine would have to be programmed, thus limiting further the hoped for greater or complete freedom for the patient's diet.